There is a strange clock in the waiting room of Lord Vetinari, Patrician of Ankh-Morpork. While this clock keeps accurate time overall, the ticks and tocks are out of sync, occasionally missing a tick altogether. The net effect is one of turning one’s brain into a sort of porridge.
Yes, a Vetinari Clock has made its way into The Hackaday Prize. This isn’t a clock that’s random yet accurate over long time spans; this is a complete replacement for run-of-the-mill clock movements you can find at any craft store.
In addition to the Vetinari Clock, [Nick Sayer]’s Crazy Clock can be programmed as a sidereal clock (3m 56s fast per day), a Martian clock (39m 36s slow per day), and a tidal clock (50m 28s slow per day), as well as some ‘novelty’ modes that still have 86400 ticks per day ranging from subtle to ‘clown car’ levels of craziness.
[Nick] is gunning for the ‘best product’ category for the Hackaday Prize, and for that he’s designing a board to be a direct replacement for the board in a Quartex Q80 clock movement. With this new board, [Nick] can replace the electronics in this movement in just a few minutes. Being built around an ATtiny45 means it’s infinitely hackable. A clock with this movement would be a great product, although judging from the video below, not one we would want to be around all day.
The clock itself is a run-of-the-mill item which uses one battery to keep time. We’re always impressed by how these dirt-cheap things remain so accurate over the long haul — but we digress. The method of attack uses coil injection to drive the hands. [Renaud] used one of the microcontrollers from the MSP430 Launchpad, along with the clock crystal which also shipped with the kit, to gain control of the mechanism. The crystal triggers an interrupt which does the actual time-keeping. The seconds hand is driven rather sporadically based on an algorithm explained in his write-up.
You can watch the uneven ticking in the video after the break. Despite that visually disturbing functionality, the short and long ticks balance each other and the correct time continues to be displayed.
Last week, we were introduced to a real-life Vetinari Clock that keeps regular time but ticks at irregular intervals. It’s a great way to turn someone’s mind into porridge, but the original build broke after a few weeks because of some limitations in the clock drive. [Simon] built a very minimal circuit does away with these problems.
Just as in the first build, a microcontroller pulses the second hand motor once every second. As for the random component of this build, the microcontroller has a puts 32 bytes into a 128 byte array. The array is checked 4 times a second, and if the byte is 1, the second hand is incremented. If the byte is 0, time stops for a little bit. [Simon] included the schematic, board layout and code if you’d like to build one yourself.
There are a few drawbacks to this design; the pattern of ticking and not ticking is hard-coded into the microcontroller. Even though the 32 second long pattern shouldn’t be noticeable by watching the clock, it’s not an entirely random solution. Judging from the comments on the original build, using radioactive decay to increment a second might be a bit uncalled for.
We would like to see a second hand that stops when you look at it though. Facial recognition, anyone?